Matthew 5:22, 29-30
22 But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.
29 And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
30 And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
These verses are part of the Sermon on the Mount. Are they aimed at Christians, and do they teach that one can lose their Salvation, or must work to earn their Salvation?
In Matthew chapter 5, there's a shift beginning in verse 20, that continues to the end of the chapter, where Christ begins revealing what it would take to be more righteous than the Scribes and Pharisees:
Matthew 5:20
20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
After this verse, the Lord begins preaching on practical moral circumstances, raising the perceived standard of the Law every step along the way.
For instance:
Ultimately, the chapter terminates with a command to be perfect:
Matthew 5:48
48 Be ye therefore perfect, even as your Father which is in heaven is perfect.
What was the launching point for all of this? Verse 20 - which recall, was in reference to the "righteousness" needed to "enter into the kingdom of heaven".
What's being taught here, then, is identical to the lesson being taught in Matthew 19:24-26, and the parallels in Mark 10:23-27 and Luke 18:24-27, which is the closing of Christ's encounter with the rich young ruler:
Matthew 19:24-26
24 And again I say unto you, It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God.
25 When his disciples heard it, they were exceedingly amazed, saying, Who then can be saved?
26 But Jesus beheld them, and said unto them, With men this is impossible; but with God all things are possible.
In this passage, Jesus did much the same thing as in Matthew 5. The man asks Jesus what "good thing" he must do to have Eternal Life (Matthew 19:16). Jesus responds that only God is good, and then tells him he must keep the commandments (Matthew 19:17-19) - which is 100% accurate in response to what "good thing" a person should do to get to Heaven.
If someone keeps all the commandments, they will be justified by the Law, and earn their own way to Heaven, as is taught also in Romans 2:13. However, in the next chapter, we see that because no one keeps the Law (Romans 3:23), all must be justified by faith rather than the Law (Romans 3:28).
This is the point Christ is trying to get the man to understand, but he doesn't get the message (Matthew 19:20). So, Christ gives him a follow-up commandment to sell all that he has, and give to the poor, and follow Him (Matthew 19:21) - something Christ knew targeted a blatant sin in the man's life.
So, what was the culmination of that passage, and the ultimate response to the man's initial question, "what good thing shall I do, that I may have eternal life?" "With men this is impossible". You cannot get to Heaven by doing some "good thing". It's "impossible".
Matthew chapter 5 likewise teaches that God's standard is higher than you will ever attain to - it's perfection (Matthew 5:48). Jesus Christ is using the Law to make "sin exceeding sinful" (Romans 7:11-13), which was its purpose (Galatians 3:19, Romans 3:19-20), with the ultimate goal that it might bring one to Christ:
Galatians 3:24
24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
The standard set by the Law is so dreadfully high, that it shows any honest man that he is doomed without the Savior. That's the point.
These passages in Matthew 5 are aimed at any "rich young rulers" in the audience. They teach the absolute truth that calling someone else a "fool" is all that God needs to condemn you. If you want to attain to that standard on your own, you better be prepared to "cut off your hand" that makes you sin, and "pluck out your eye" that makes you sin, because that's the only way a man can escape Hell fire on his own merits. Good luck.